Prior to the present invention, in the railroad industry it has been well known for many years to use standard couplers which were approved by the Association of American Railroads (AAR) to connect together adjacent ends of a pair of railway cars. In this application, for example, such couplers are designed to facilitate both the connecting and disconnecting of individual railway cars. These couplers enable such cars to be readily combined to make up a train consist, or to be individually separated, as required, for loading and unloading purposes.
In more recent times, however, such railroad industry has discovered that the interconnecting of several railway cars to form a generally semipermanent unit has a number of important advantages. Particularly, for example, railroad cars adapted for use in "piggyback" service have been joined in this manner to advantage. The railroad cars which are joined in such semipermanent fashion are commonly referred to in the railroad industry as a "10-pack". These 10-pack units do not require the use of the standard coupler, except between units. The primary reason such standard couplers are not required is because these 10-pack units are only broken periodically. Normally, this occurs when maintenance of an individual component must be carried out. Obviously, considerable cost-savings are achieved by this semipermanent coupling arrangement. These cost-savings are mainly derived from lower car weight, fewer railway trucks, reduced maintenance, and generally lower equipment cost. Such lower equipment cost being achieved by elimination of draft gears and a reduction in the number of trucks required.
With the use of these semipermanent coupling arrangements and with the higher loads presently being carried by modern railway trains, it is of the utmost importance that a close-buttoned relationship be maintained between the numerous coupler draft components. Such close-buttoned relationship is required to reduce the effects of the impact forces which are encountered by a car under buff conditions of train operations.
One prior type of articulated coupling device used for the purpose of connecting adjacent ends of a pair of railway cars, in a semipermanent manner, is taught in U.S. Pat. No. 4,258,628. This particular articulated coupling device includes a male connection member secured to one end of a first railway car body, and a female connection member secured to an adjacent end of a second railway car body. The female connection member, in this arrangement, is rotatably-engaged in a center plate bowl of a bolster of a railroad car truck in a manner that is well known in the railway art. The outer end of the male connection member is disposed for movement in a cavity formed in the outer end of such female connection member. Both the male and female connection members are joined, in a semipermanent manner, by a pin member. One important disadvantage in this arrangement is that this pin member is positioned in a vertical direction and disposed in aligned apertures formed in each of the male and female connection members. The aperture formed in the male connection member for receiving the pin member must be somewhat larger than the pin member itself to allow certain required movements. A rear surface portion of the aperture formed in the male connection member for receiving the pin member has a horizontal concave configuration and a vertical convex configuration. This configuration enables both the male connection member and the female connection member to move in each of a horizontal direction and a vertical direction in relationship to one another while, at the same time, providing a relatively substantial area of surface contact between the rear surface of the pin aperture and the pin member.
Another disadvantage in this coupling arrangement is that the outer end surface of the outer end of the male connection member must include a convex configuration which abuts against a complimentary concave surface formed on a front face of a follower member. In this coupling device, the follower member is carried within the rear portion of the cavity formed in the other end portion of the female connection member. A pair of vertically-disposed, slot-like cavities are formed on the rear face of such follower member. Each of these vertical slots has a resilient element disposed therein which protrudes outwardly from such follower member. The exposed outer surface of each such resilient element is engaged by a vertically-disposed wedge element. Such wedge element is provided to urge the follower member and the male connection member forward. In this manner, the rear surface portion of the aperture formed in the male connection member is maintained substantially in contact with the pin member at all times.
Such contact is necessary in these prior art articulated coupling devices, because most of the articulated connecting parts are cast members. In order to reduce the cost of this coupling device, the cast members receive very little, if any, finish-machining to provide the necessary or desired dimensional control. As a result of this, it is rather difficult to provide an articulated coupling device which is self-adjusting under various wear conditions to minimize the slack in the various connections encountered during, service. Other prior art articulated coupling devices are taught in U.S. Pat. No. 3,716,146 and Canadian Patent No. 1,231,078.